New iron-tungsten oxide composition



United States Patent This invention relates to a new iron-tungsten oxide compound, Fe WO and to methods for its preparation.

In another aspect the invention relates to solid solutions of this compound.

It is an object of this invention to provide a new metal oxide of iron and tungsten wherein the tungsten is present in the hexavalent form.

It is another object of this invention to provide meth ods for the preparation of this new compound.

A still further object of the invention is to provide a new iron-tungsten metal oxide which has a novel inverse columbite structure.

Another object of the invention is to provide solid solutions of the new iron-tungsten oxide, Fe WO Other objects and aspects of the invention will become apparent from a-consideration of the accompanying disclosure.

Several synthetic crystalline compounds are known which have a columbite-type structure. Columbite represents a family of minerals with a similar structure (Fe, Mn) (Ta, Nb) O Synthetic columbite-type compounds which are known include FeNB O and ZnTa O All of these compounds are of the type A +B +O According to the present invention, I have now found a new columbite-type compound of the formula Thus, the B ion is hexavalent and the positions of the A and B ions in the lattice are therefore interchanged. The structure can thus be interpreted as an inverse columbite structure. Thus, this is an entirely new type of crystalline compound.

According to the invention, the new compound is prepared by intimately admixing Fe O and W compacting the powdered mixture into a cohesive mass, and thereafter heat-treating the material, preferably in a nonreducing atmosphere at a temperature above about 750 C. The upper limit of preparation should be held to about 950 C., and in any event, below the temperature at which an undesirably high rate of decomposition of Fe WO occurs. Thus, the compound is decomposed almost completely to Fe O after firing for 100 hours at 1100 C. A practical upper limit is usually around 950- 1000 C. In actual practice an oxidizing atmosphere is usually employed, such as air. Times of preparation can be from 2 to 30 hours, usually from to 20 hours, although shorter or longer times than these ranges can be used. If too short a time is used, the yield is merely lowered; too long a time is merely unnecessary.

In preparing the compound, it is desirable that equimolar ratios of Fe O and W0 be employed in order to obtain a product substantially free from contamination of one or the other of the starting materials. However, ratios above or below the ideal ratios can be used, it be ing understood that the purity will be lowered. In preparing the compound, the powdered starting materials are desirably 30 microns or finer.

In a series of specific examples of the invention, equimolar portions of Fe O and W0 each in finely divided powdered form passing through a 20-mesh screen, were fired at temperatures of 600, 700, 760, 850, 900 and 950 C. for 20 hours. The sample at 760 C. showed by X ray powder diffraction data that the reaction had begun but was not complete, while the lower temperature sam- 3,165,419 Patented Jan. 1 2., 1965 ples did not indicate any substantial reaction.- Therefore, for temperatures of 750 or 760 C. it will be apparent that a longer time is required for complete reaction. The samples above this temperature showed substantially complete reaction in the X-ray powder diffraction data since neither of the starting materials was detected by the X-ray technique.

In Table I, the X-ray powder diifraction 'data are shown:

TABLET X-ray Powder Difiraction Data z=superstructure reflections.

The compound had an orthorhombic unit cell, space group P Z=4.

The x values in the third column are superstructure reflections which first were apparent in samples prepared at 850 C. and were strongly present in the samples prepared at 950 C. The superstructure reflections were not present in the sample prepared at 760 C. Table II shows the lattice constants for the primitive or disordered unit cell, ignoring the superstructure formation.

TABLE II Lattice Constants (A.U.)

an b 13.75 5.57

The density of the compound calculated from the X-ray data was 6.66 grams per cubic centimeter, while the experimental density determined by pycnometer techniques was 6.43 grams per cubic centimeter. The color of the compound was a rich dark brown.

By compressing Fe WO and rutile (TiO mixtures, powdered to below 20 microns, into coherent form and firing these at 700 C. for 20 hours, a series of solid solutions having a rutile structure were formed. The lattice constants were a =4.64 A.U.; c =2.98 A.U. for the solid solution formed between three mols of rutile and 1 mol of Fe WO Thus, the unit cell of rutile is slightly increased. The solid solution of 1 mol of Fe WO and 2 mols of TiO was similarly formed and had very slightly larger lattice constants. Thus, I have also found that my new compound can form a solid solution with Ti0 (rutile) wherein the Fe WO is about one-third or less of the solid solution. These solid solutions appear black.

Similarly, solid solutions of Fe WO were formed in n3 v Cr WO These solid solutions have an inverse trirutile structure and-were prepared by mixing thepure oxides in finely divided form in the desired molar ratios, pressing and firing at 960 C. for 20 hours; After quenching to room temperature, the samples were investigated by X-rays. Thus, it was found that the inverse trirutile (Cr WO could take up to 3 mols of Fe WO into solid solution having theinverse trirutile structure. These had preparation and properties of Cr WO are set forth in copending application S.N. 52,778, filed August 30, 1960, now US. Patent 3,070,422. This compound can be prepared by mixing powders of Cr O andWO' in equimolar ratios, compacting and firing at 1000 C. for 20 hours.

The new compound and solid solutionsof this invention are useful particularly as ceramic'coloring agents in enamels, glazes, and paints and as fillers and coloring agents in plastics such as polyethylene and polystyrene. In the plastics, they can be employed in amounts of 0.5% to 10% or even more, being milled with the plastics in finely divided form.

The new compound can be used, for instance, in the following paint formula.

Ingredient: Lbs. Fe WO m- Zinc oxide 25 Long-oil-soya alkyd resin (60% nonvolatile) 480 Mineral spirits 181 Cobalt naphthenate (6% Co) 3 Lead naphthenate (24% Pb) 3 Calcium naphthenate (4% Ca) 2 Total 9 9 1 Either of the solid solutions of the invention can be substituted in the above paint formula.

I line structure.

As will be evident to those skilled in the art, various modifications of this invention-can bemade or followed in the light of the foregoing disclosure and discussion without. departing from the spirit and scope of the a disclosure or from the scope of the claims.

I claim: i 1. The-compound Fe WO 'in solid solution in rutile in an amount up to one-third mol fraction of the solid solution, said solid solution having ,a rutile type crystalline structure.

7 2. The compound Fe wO in solidsolution irrCr WO in an amount up to 3 mols of saidcompound to 1 mol' of Cr WO said solid solution having a rutile-type crystal:

3. The compound Fe WO in s'olidsolutionin rutile, in an amount between about 1 mol of Fe WOg to 3 mols of rutile and about 1 mol of Fe WO to 2 mols'of rutile, said solid solution having a rutile type crystalline structure.

' OTHER REFERENCES Kozmonov: Zhur. Fiz.Khim., volume 31, pages 1861-. t 1865 (1957) [Chemical Abstracts, volume 52, 6038i].

' Theoretical Chemistry, Longmans, Green and Co., New

York,'vol. XI, pages 678 and 801 (1931). 

1. THE COMPOUND FE2WO6 IN SOLID SOLUTION IN RUTILE IN AN AMOUNT UP TO ONE-THIRD MOL FRACTION OF THE SOLID SOLUTION, SAID SOLID SOLUTION HAVING A RUTILE TYPE CRYSTALLINE STRUCTURE. 